In automatic transmissions of a motor vehicle, there are transmission control modules for controlling the coupling and switching operations that are installed in the oil-filled interior space of the transmission. For the electronics, the transmission control modules generally have a fluid-tight housing of their own for the Transmission Control Unit (TCU), the power electronics and for example a circuit on leadframes (DBC, Direct Bonded Copper). The electronics are protected in the form of a thermoset molded housing or a steel housing or by means of a plastic cover with seals with respect to the rest of the transmission control module housing. In the case of flexible or rigid circuit boards, FPCs or PCBs, as the module construction and connection technology (packaging), these packagings have a cutout for the transmission control unit, in order that the transmission control unit can be adhesively attached in a heat-conducting manner on a carrier plate in this cutout or can be held down on it by a spring.
Transmission control units with steel housings generally have very complex pin lead-throughs in the form of glazed-in Ni—Fe pins and expensive housing parts. Furthermore, in terms of the geometry, the construction is very high, that is to say bulky, since the pins come out of the housing vertically instead of horizontally. On the other hand, the seal-tightness is very good. If required, the entire transmission control unit is subjected to what is known as a burn-in or high-low temperature test. The positioning and holding down of the TCU, transmission control unit, in the transmission takes place by means of a spring, in order that the transmission control unit is pressed against a cooling transmission component, such as for example a hydraulic plate, in a way that provides good heat conduction.
In the case of transmission control units that are encapsulated with a potting compound, known as molded TCUs, the circuit carrier (HDI-PCB, LTCC) must be adhesively attached onto a metal or ceramic plate and complex leadframe parts must be placed around the circuit carrier of the transmission control unit. Furthermore, bonding connections, that is to say electrically conducting connections, must be produced between the circuit carrier and this leadframe. This is followed by placing the transmission control unit in what is known as a molding tool for the encapsulation. After the encapsulation (molding), the leadframe must be punched free in the outlet from the molding compound, i.e. potting compound, in order that individual pins are created. The pins subsequently have to be laboriously cleaned and tin-coated.
The transmission control units (TCUs) with a plastic cover are sealed with respect to a flexible module film (FPC) by a sealing ring or an adhesive joint to intercept as far as possible at the edge of the cover any oil that may nevertheless penetrate. Because of potential problems with the seal-tightness between the cover and the FPC, or FPC or carrier plate, and to avoid a possible thermal pumping effect of an air space under the cover, the interior space of the cover and of the housing is laboriously filled with a gel.
In the case of integrated transmission control units potted with a potting compound, a bare-die circuit is completely potted with a potting compound of epoxy resin, polyester, polyurethane, etc. on an HDI-PCB, that is to say a rigid circuit board or an LTCC ceramic.
DE 10 2013 215 246 A1 describes an electronic module with circuit boards and a plastic sealing ring that can be molded on by injection molding, in particular for a motor vehicle transmission control unit, wherein a microstructuring is formed peripherally in the form of a ring in each case on the outer circumference of a first circuit board element and a corresponding peripheral microstructuring in the form of a ring is formed on the outwardly directed surface of the second circuit board element, which by means of a sealing ring produces a form-fitting connection both with the microstructuring formed on the first circuit board element and a form-fitting connection with the microstructuring formed on the second circuit board element.